Technical Abstract:
Microbial communities play a critical role in agricultural ecosystems. In fungal-fungal associations, an organism can produce metabolites that elicit a physiological response in other organisms, thereby affecting the outcome of the interaction. Understanding this communication process may be critical to maximize crop disease control and therefore crop production. Small, cysteine-rich proteins, synthesized by plants, fungi, viruses and bacteria, can serve as antimicrobial peptides and be an integral part of their defense system. One of these proteins, KP4, produced by the Ustilago maydis P4 virus, inhibits growth of other fungi, including Fusarium and Aspergillus, by blocking calcium ion channels. The mature KP4 protein is 105 amino acids and contains 10 cysteine residues. Here, analysis of publicly available genomic sequence identified 37 KP4-like genes from a range of Ascomycota, a Basidiomycota, and the moss Physcomitrella patens. Six of the genes encode a homodimer with the two KP4-like domains in tandem. Sequence comparison and phylogenetic analysis of the corresponding proteins/domains provides insight into the evolutionary history of the KP4 family and evidence for lateral gene transfer between kingdoms. The data also suggest that formation of the KP4 homodimer occurred independently in different lineages of the Ascomycota. Understanding the nature and function of KP4-like proteins in mycotoxin-producing species of Fusarium may help to limit plant diseases and increase food safety and food production.